Switching system for electric currents



June 1941- A. w. LUNDSTROM SWITCHING SYSTEM FOR ELECTRIC CURRENTS Filed June 11, 1940 w W n ww v t 0 n aw A V I by W4 Patented June 17, 1941 UNITE D STATES OFF-12C E SWITGHING SYSTEM'FOR EIiECTRIC GURREN'DS Axel Lundstrom, Drexel Hill, Pa., assignor to General Electric. Company," at corporation of' New York 9 Claims.

My invention relates to improvements-"in switehing systems for electric currents and more particularly to switching systems for selectively connecting a given circuit to-anyone ofaplurality of sourcesof electric current but to only one of the ources at a time. 'I-he principal object of my invention isto provide" an improved switching systemsuch that a given circuit may be connected atany time to only one of a plurality of sources whereby to avoid thenecessity for synchronizing operations; This and otherobjects of my invention will appear in-moredetail hereinafter.

When ships'aredockedfor any-lengthof time,- it maybe desirable; for reasons of economy-in fuel and-reduction of the mechanical operating staff; to connect the shipslig-hting load-,- auxiliaries-andthelike, to'a source on-shore.- isparticularly the case duringrepairs; replacements and the-like, of shipsmechanical'equipment especially when the ship is in drydock. Sinceasingle shore source may fall, it portant to have anotheremergency source upon which" to rely. If the sources are alternating current sources, thenno-two or more of =them can be connected to the same circuit withoutdanger unless they are in synchronism. This synchronizing requirement tends to more com-- plicated and costly controls whichit is desirable to avoid; if possible, for reasons ofeconomy andsimplicity. It is accordingly, importantthat a load circuit cannot be-connected-totwo-sources at'the" same'timebut that it may be selectively connected to theships-source, a preferred shore source; or an emergency source, as desired,- but to-only one of these at a time. Equipment forthis purpose must be-economical in cost, simple to'operate, and rugged in structure.

In accordance with my invention, I provide an improved switching arrangement wherebya load circuit may be connected to any one of' a plurality of sources ofelectric current but to only one-of thesesource at a time through suit able and yetrelatively simpleand economical interlocking arrangements such' that" no two switches can be so operated as to be in the'closed position at the same-time and yet tha-tthe circult may be supplied from any one of thepluralltyof sources selectively asdesired andin case offailure of a particularsource.

My invention will be better understood from the-- following description when considered in connection with the accompanyingdrawing; and its scope will be pointed out in the appended claims:

ranged to, beconnected to any one of three sources of alternating current, schematically: in-- dicated by conductorsl, 3. and 4, butto only one of these sources at a time; For convenience in differentiating the sources 2; 3 and 4, they will hereinafter be designated the normal, preferred andemergency sources. Source 2, for example; maybe aships source, source 3 a preferred shore source,-and ource 4 an emergency source, which may also-be on shore. For connecting the circuit l, which may be the ships load circuit or bus,:to the 'ships source 2, I provide suitable switching means indicated asa latched closed circuit breakeri which is provided with trip and closing coils-6 and 6 respectively, and an aauxiliary switch 1. Further, in accordance with my invention, the-circuit breaker 5 is provided with suitable meansi'or maintaining it in the open position-oncethat it has been tripped. As shown, thisv means comprises a coil 8' cooperating with the tripping coil 6 to prevent the reclosing of the circuit breaker; The circuit breaker i-isofthe conventional trip-free type and cannot be mo mentarily closed, either manually or electrically as long asthe-closing prevention coil B is-energized.

For connecting the load circuit I to each of the other sources 3 and 4', I provide suitabl switching means 9 and I0; respectively, which are schematically illustrated a circuit breaker of the typedisclosed' in United States Letters Patent 2,047,842 issued July 14, 1936' and assigned to the-assignee of this invention. As shown,- these circuit breaker Sand H] have operating handles II, which are in the lower position, asshown when thecircuit breaker is open and in then!)- per position; notshown. when the circuit breaker is closed.

In orderto prevent the simultaneous connection oftwo or more sources to the circuit I; I provide a control mechanism whichincludes movable means operative in one position to prevent the closing operation of both of the switches 9 and I0 and in either of two other positions to permit a closing operation of one or the other of' these two switches only after effecting an opening operation of the circuit breaker 5. As illustrated; this movable means comprise an operating'handle' I2; mounted onxa shaft l3 one end ofwhich is suitably 'journaled in" a plate l4 secured totheswitchboardli and'the other end.

a slotted crank H which engages a pin I8 ex-' tending through an opening IS in the switchboard into the bar It. This bar may be suit ably guided on the switchboard, and for this purpose it may be a channel member, as shown,-

whose lower flange engages blocks 28 suitably secured to the switchboard l5 and whose upper flange engages suitable resilient shoes 2il..

In order to insure the opening of the circuit breaker 5 before either of the switches '9' or can be closed, the movable means further includes suitable switching means comprising cooperating contacts 2l, 22, 23, 24, 25, and zfiwhich may be operated to the closed and openpositions bycam means 27, 23 and 29 suitably. disposed onsthe shaft 13 as, for example, in the manner shown in the drawing. The switchin means. are so arranged that, upon movementof .the handle l2 either to the rightor to theleft of the position shown to efiect movement of. the

bar [6 so as to permit the closing operation of the switches It or 9 respectively, the trip coil 6 of, the circuit breaker is energized and also the,

maintaining coil 8. whereby to effect opening of the circuit breaker and to prevent ,reclosing thereof as long as the coil 8 is energized. This coil, will be energized during the continuation of, energization of the source 3, or Awhile the operating handle is in position either tothe left of the ofi position shown or to therightof the pfi position. For auxiliary tripping pur: poses the circuitbreaker 5 may have itstrip circuit controlled through suitable switching means 30 which may be of any type, examples of which are well known to the art. 7 Assuming the parts positioned as shown in, the drawing and that it is desired to disconnect the load circuit or bus I from the source 2 and cone meet it to the source 3, then the operating handle I2 is turned counter-clockwise or to the left as viewed in the drawing. In consequence of such counter-clockwise rotation of the operating hang. dle, the contacts 2i are closed to completethe circuit of the trip coil 6 from a positive control bus through a conductor 3 l, the auxiliary switch 1, the trip coil 6, a conductor 32, the contacts 2|. and a conductor 33 to a minus control bus. Simultaneously with the closing of the contacts 2| the contacts 23 and 25 are closed tocomplete the circuit of the closing preventing coil 8 across one phase of the source '3 on the source side of the switch 9 as follows: the center one of the conductors 3, a conductor 34, the contacts 23, a conductor'35, the closing preventing coil 8, a conductor 36, the contactszi, and a conductor 31 to the right hand conductor 3. In consequence of the energization of the coils 6 and fi, the circuit breaker 5 is opened and prevented from closing aslong as the source 3 is energized and the contacts 23 and 25 are closed. Since the interlock bar It is now moved to the right to clear the operating handle H of the circuit breaker 9, this circuit breaker may be closed to connect the preferred source 3 to the 'load'bus l. The "operation of switching the load bus I from the source 2 to the source 4 is similar to that described except that the operating handle I2 is moved to the right to close contacts 22, 24 and 26 and thereby energize the trip coil 6 and the closing preventing coil 8 which, in this case, is energized from one phase of the source t through conductors 3B and 39 in a circuit which will be obvious from the drawing. It'will be apparent from the foregoing that any time when the load circuit I is connected to either the source 3 or to the source 4 it may be switched from one to o'neextre'me position to the-other extreme position to move the interlock bar it clear of the circuitbreaker which it is desired to close to connect the source in question.

Any attempt to close the circuit breaker 5 during the movement of the operating handle l2 from one extreme position to the other will not make it possible to efi'ect a closing operation of either of the switches Band Ill with the circuit breaker closed since the moyement of the operating handle to such position will, as before described efiect the opening ofthe circuit breaker and keep-it open as long as the operating handle remains in the x rem pos ons While I have shownand described my inventionin considerable detail, I do not desire to be limited to the exact arrangements shown. but, seek to cover in theappended claimsall those modifications that fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letter-s Ratent of the United States is:

1.; I n combination, a circuit, a plurality of sources of electric current, a first switch for connecting said circuit to one of said sources, andmeansfor connecting said circuitto another of said sources ,only when said first switch is open comprisinga switch for said other source and means movable to one position for preventinga closi ng operation of said other switchand movable to another position for eifectingan openingoperation of said first switch and sub: sequently permitting operation of said other. swi -v 2. In combination, a circuit, a plurality of sources of electric current, a first switch for connecting said circuit, to one of said sources, means for connecting said circuit to another of; said sourcesonly when said first switch is open comprising a switch for said other source and means movable to one position for preventing aclosingoperation of said other switch and movable to another position for effecting an opening. of said first switch and subsequently permitting operation of said other switch, and means for preventin gthe closing of said first switch while said movable means is in said'other position. 7

v 3. In combination, a load circuit, three sources of electric current, a circuit breaker for connectingsaid load circuit to one of said sources, and means for tripping said circuit breaker and for connecting saidlload circuit to either of the other two sources only when said circuit breaker is "open. comprising two switches and a control mechanism operative in one position mechanically to interlock both of said switches in the circuit opening position and to either of two other positions to effect the energization of said tripping; means and to remove the interlock from one of said switches.

4. In combination, a circuit, three sources of electric current, a first switch for connecting said circuit to one of said sources, means for connecting said circuit to either of the remaining two sources only when said first switch is open comprising a switch for each remaining source and a control mechanism including movable means operative in one position to prevent a closing operation of both of the remaining source switches and in other positions to permit operation of only one of said remaining source switches only after efiecting an opening of said first switch; and means for maintaining said first switch open while said movable means is in any one of said other positions.

5. In combination, a load circuit, three sources of electric current, a latched closed circuit breaker for connecting said load circuit to one of said sources, tripping means for releasing said latched closed circuit breaker to eliect the opening thereof, means for subsequently maintaining said tripping means in the tripping position, and means for connecting said load circuit to either of the other two sources only when said circuit reaker is open comprising two switches and a control mechanism including a movable member operative in one position mechanically to interlock both of said switches in the circuit opening position and to either of two other positions to effect the energization of said tripping means and the operation of said maintaining means and to remove the interlock from one of said switches.

6. In combination, a load circuit, three sources of electric current, a circuit breaker for connecting said load circuit to one of said sources, electromagnetic means for effecting the opening of said circuit breaker and subsequently preventing the closing thereof, and means for effecting the energization of said electromagnetic means and for connecting said load circuit to either of the other two sources only when said circuit breaker is open comprising two switches and a control mechanism including a movable member operative in one position mechanically to interlock both of said switches in the circuit opening position and to either of two other positions to effect the energization of said electromagnetic means and to remove the interlock from one of said switches.

7. In combination, a load circuit, three sources of electric current, a circuit breaker for connecting said load circuit to one of said sources, and means for effecting the opening of said circuit breaker and maintaining it open and subsequently connecting said load circuit to either of the other two sources comprising two switches and a control mechanism including a movable member 0perative in one position to prevent a circuit closing action of both of said two switches and movable from said one position to either of two other positions to effect the opening of said circuit breaker and to maintain it open while in such other position and to permit the closing of one of said two switches.

8. In combination, a circuit, three sources of electric current, a first switch for connecting said circuit to one of said sources, and means for connecting said circuit to either of the remaining two sources only when said first switch is open comprising a switch for each remaining source and a control mechanism including movable means operative in one position to prevent a closing operation of both of the remaining source switches and in other positions to permit operation of only one of said remaining source switches only after eifecting an opening of said first switch.

9. In combination, a circuit, three sources of electric current, a first switch for connecting said circuit to one of said sources, and means for connecting said circuit to either of the other two sources only when. said first switch is open com prising two switches, and a control mechanism including movable means operative in one position to prevent a closing operation of both of said two switches and in either of two other positions to permit a closing operation of one or the other of said two switches only after effecting an opening operation of said first switch.

AXEL W. LUNDSTROM. 

